Proposed New Tunnel between NJ and Queens

What would be the technical feasibility, if anyone were even talking about it, of running a that tunnel under Kill Van Kull into Staten Island and then another tunnel under the bay to Brooklyn? Would building such a system cost significantly more than the proposed tunnel between Greenville Rail Yard and the 65th Street Rail Terminal?

If done properly, it might be a mileage diversion for freight, but would allow for future alternate public transporation routes for PATH while providing the possibility that Staten Island gets proper access to NYC transit. It could even be designed to link up with future PATH extensions (to Newark International, for instance) and Pataki's plan for a "one-seat" ride from Kennedy to downtown Manhattan. I suppose the tunnel (or tunnels) would need to be wide enough to accomodate separate freight, PATH, and subway tracks to be efficient.

I suppose a big hurdle would be at-grade right-of-way in both NJ and Staten Island. I'm not too familiar with Staten Island geography, but I'm guessing there's a good chance there isn't an overland right-of-way, and condemning one for what would probably have to be a 6-8 track system would be difficult.